An electrostatographic reproduction apparatus, such as electrophotographic printers or copiers, produce image reproductions by transferring pigmented polymeric toner particles to a receiver member from a primary imaging member. An electrostatic latent image is initially formed on the primary imaging member using known techniques, and developed into a visible image by bringing the primary imaging member into close proximity with toner particles, also referred to as marking particles. The toner particles are image-wise attracted to the primary imaging member, thereby forming a visible image on that member. The image is then transferred to a suitable receiver member such as paper, generally upon application of an electric field that urges the toner particles from the primary imaging member to the receiver member. The toned image is then permanently fused (fixed) to the receiver member by subjecting the receiver member to heat and pressure, such as by sending the receiver member through a pair of heated rollers. In order to facilitate release of the toned receiver member from the fuser roller, the fuser roller is generally coated with a thin layer of a release agent, for example generally some sort of silicone oil.
In order to form duplex images, whereby toned images are produced on both sides of a receiver member, it is generally necessary to flip a previously toned and fused receiver member to allow the toned image on the primary imaging member to contact the untoned side of such receiver member. This, however, allows the release agent on the receiver member from the first fusing step to transfer to any contacting elements in the electrostatographic reproduction apparatus. U.S. Pat. No. 5,406,364, issued on Apr. 11, 1995, by Maeyama et al. teaches that porous particles can absorb release agent to clean contaminated surfaces in an electrophotographic apparatus. A cleaner in the form of a web is prepared by immersing a piece of non-woven fabric into a colloidal solution of alumina sol. Polyvinyl alcohol may also be used. The web is used to remove silicone oil from a transfer drum.
It is obvious that in sheet-fed electrostatographic reproduction apparatus, as opposed to a web-fed machine, sheets of the receiver member need to be transported from a holding reservoir for unused receiver members, through the reproduction apparatus, to a bin wherein the image-bearing receiver members are held until they are removed, for example by an operator. Alternatively, the receiver members can be transported into some sort of finishing station such as a collator, folder, etc.
In applications requiring the formation of multi-color images, a plurality of different color toners are used. These different color toners necessitate the formation of separate electrostatic latent images on the primary imaging member and the development of respective electrostatic latent images with the proper colored toner. For example, in full-process color, latent image separations and toner colors corresponding to the subtractive primary colors, cyan, magenta, yellow, and black, are used. These separations must ultimately be transferred to a receiver member in register in order to form the multi-color image reproduction.
In many multicolor electrostatographic or electrophotographic reproduction apparatus, transferring separate colors to a receiver member is accomplished by wrapping the receiver member around an electrically biasable drum. The electrostatic latent image, which had been formed on separate areas of the photoreceptor that correspond to the periodicity of the drum, are each rendered into visible images using the separately colored toner particles. These images are then transferred, in register, to the receiver member. This process, however, has a complicated receiver member path, as the receiver member must be picked up and held by the transfer drum and then released back to the transport mechanism at the appropriate time. This process can be simplified by, first transferring all the separate images, in register, to an intermediate transfer member and then transferring the entire image to the receiver member. In either of these two modes of operation, the output speed of the electrostatographic reproduction apparatus is reduced due to the number of sequential transfers that need to be done.
In another example of color electrostatographic reproduction apparatus, it is preferable to separate the color separation image formation mechanism into separate, substantially identical, modules. This allows each colored image to be printed in parallel, thereby increasing the speed of the reproduction apparatus. In this embodiment, the receiver member is transported from module to module and, while it can be picked up and wrapped around a transfer roller, there generally is no need to do so. Again, it is preferable to first transfer each image to an intermediate transfer member, preferable a compliant transfer intermediate member as described in U.S. Pat. No. 5,084,735, issued on Jan. 28, 1992, by Rimai et al. In order to reduce the time needed to produce a printed image, it is preferred, however, that each color be produced in a separate module comprising a primary imaging member, development station, and transfer apparatus.
In all embodiments, it is necessary to transport the receiver member through the electrostatographic reproduction apparatus. A preferred mode of transport utilizes a transport web, preferably a seamless transport web, to which a receiver member can be attached electrostatically or by any other well known mechanism. When such transport web is employed, in order to facilitate registration of individual developed images on a receiver member, it is preferable to drive all the image forming modules by friction, especially in the case where separate modules are used for the formation, development, and transfer of individual color separation images. This requires that the web have a sufficiently high coefficient of friction during operation. Although many materials may have sufficiently high frictional coefficients initially, the presence of fuser release agents on the receiver member transport web can reduce the friction with usage and result in slippage in a frictionally driven electrostatographic reproduction apparatus. This can result in image defects such as misregistration and general overall unreliability of the reproduction apparatus.